1. Field of the Invention
The present invention relates to a robot for use in a vacuum chamber of a lithography apparatus.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic apparatus can be used, for example, in the manufacture of flat panel displays, integrated circuits (ICs) and other devices involving fine structures. In a conventional apparatus, light is directed to a patterning device, which can be referred to as a mask, a reticle, an array of individually programmable or controllable elements (maskless), or the like. The patterning device can be used to generate a circuit pattern corresponding to an individual layer of an IC, flat panel display, or other device. This pattern can be transferred onto all or part of the substrate (e.g., a glass plate, a wafer, etc.), by imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate. The imaging can include the processing of light through a projection system, which can include optical components such as mirrors, lenses, beam splitters, and the like. Other components or devices can exist in a lithographic apparatus that can also contain optical components, such as a multi-field relay (MFR), which contains optical components to divide a radiation beam into a number of individual beams prior to patterning.
Many conventional lithographic apparatus, such as those used in extreme ultra-violet (EUV) photolithography applications, position various components of the apparatus within a vacuum chamber, including patterning devices, substrates or wafers, and additional optical components such as numerical apertures. In such a scenario, a robot can be placed inside the vacuum chamber to transport or move these components within the vacuum environment.
In general, conventional robots suited for use in atmospheric-pressure lithographic apparatus are ill-suited for used within a vacuum environment. These conventional robots often feature bearing assemblies lubricated with hydrocarbon compounds. In an effort to render these robots more amenable for in-vacuum use, the bearing assemblies and are often lubricated with specialized “vacuum grease” formulated to minimize out-gassing of molecules from 0 to 100 atomic mass units (a.m.u.). Further, conventional robots for in-vacuum use often feature ferro-fluidic seals, which also outgas hydrocarbon molecules into the vacuum environment.
Unfortunately, EUV photolithography applications, and some other applications, require minimal out-gassing of lubricant molecules from 0 to 200 a.m.u., as these molecules may condense onto sensitive EUV optics, severely limiting their lifetime For such applications, conventional robots utilizing “vacuum grease” and ferro-fluidic seals are unsuitable for use in vacuum due to out-gassing of large lubricant molecules, especially above the 100 a.m.u. threshold.